I've also had a situation like drbill that got out of my control. Severe currents one day on the Spiegal Grove. We were lectured at the beginning of the dive, not to let go of the rope because the currents were so strong, we could very quickly be pulled away. The currents were so strong that it took a lot of strength just to hang onto the line on the surface. My dive buddy had jumped in and was hanging onto the tag line waiting for me, but she had to abort. She was trying to switch to her snorkel, but couldn't find it and swallowed a bunch of water. I was in the water, waiting for the next couple and I was going to dive with them. I let them go up the granny line first. Then I put myself inside the granny line next to the boat as I thought, if the current pulls me away from the rope, I won't be carried off in the current. I had no way of foreseeing what would happen next.
As I was pulling myself along, I heard the woman screaming, "I can't breathe" and they were very quickly headed for me with the current. I lifted the rope over my head to get outside the granny line, but they were tugging hard on the line and it got caught behind my head between my head and the tank. Then they were both practically on top of me and she was screaming "get out of my way." I couldn't. The rope was being pulled even harder against my neck and I started saying "I'm tangled and I can't breathe." I put my reg in my mouth and grabbed the rope and held it away from my neck, and with the other hand, grabbed further up the rope to take the pressure off. I relaxed my legs, so they were carried behind me, they were out of the way and I was on my back, just hanging on. They managed to get around me and out of the water, but I was left tangled in rope. I tried to twist to get out, but just made the worse, I couldn't tell the right direction to turn. I followed the instructions of the DM on the boat to untangle. I never thought at any time that I would not get out of the situation. I never felt panicked, but I was too exhausted to try and dive.
My dive buddy starts lecturing me about how I didn't get out of the way, the next thing I know there is a generic lecture on the boat about not twisting around and getting tangled in the rope. I thought - didn't you guys just see what happened? But I didn't say anything, I just thought it would look worse if I did, but I was a little miffed. If I made a mistake, it would have been getting inside the granny line, but it seemed like a good idea at the time. Live and learn I guess.